Background: Goal tacrolimus concentrations for the prevention of rejection in sensitized renal transplant recipients are not well established.
Methods: We evaluated the association between discharge tacrolimus trough concentration and the incidence of biopsy-proven acute rejection (BPAR) in 216 moderately sensitized renal transplant recipients (negative flow crossmatch and positive donor-specific antibodies) treated with tacrolimus.
Results: At transplant, the mean±standard deviation (SD) peak panel-reactive antibody was 60±33 and median donor-specific antibody level was a mean fluorescence intensity of 710 (interquartile range, 328-1202). The mean±SD tacrolimus trough concentration at discharge (median postoperative day, 5; interquartile range, 4-7) was 7.6±3.7 ng/dL. Patients were divided into two groups based on a discharge tacrolimus trough concentration of 8 ng/mL. Baseline characteristics were similar between groups. Thirty-four (28.6%) of the 119 patients with a tacrolimus trough concentration less than 8 ng/mL and 19 (19.6%) of 97 patients with concentrations of 8 ng/mL or greater experienced BPAR during a median follow-up of 14±4.7 months (P=0.04). Adjusting for age, race, donor status, and peak panel-reactive antibody, a discharge tacrolimus trough concentration less than 8 ng/mL was significantly associated with a higher risk of BPAR (hazard ratio, 1.84; 95% confidence interval, 1.04-3.25; P=0.04). Serum creatinine, cytomegalovirus, BK viremia, or BK nephropathy at 1 year did not differ between groups.
Conclusions: In a patient population predisposed to BPAR, discharge tacrolimus trough concentration less than 8 ng/mL was associated with a nearly two times greater risk of BPAR.